Как создать собственную модель?

class CurrencyModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    CurrencyModel(QObject *parent = 0);
 
    void setCurrencyMap(const QMap<QString, double> &map);
    int rowCount(const QModelIndex &parent) const;
    int columnCount(const QModelIndex &parent) const;
    QVariant data(const QModelIndex &index, int role) const;
    QVariant headerData(int section, Qt::Orientation orientation,   int role) const;
 
private:
    QString currencyAt(int offset) const;
 
    QMap<QString, double> currencyMap;
};

#include "currencymodel.h"
 
CurrencyModel::CurrencyModel(QObject *parent) : QAbstractTableModel(parent)
{
}
 
int CurrencyModel::rowCount(const QModelIndex & /* parent */) const
{
    return currencyMap.count();
}
 
int CurrencyModel::columnCount(const QModelIndex & /* parent */) const
{
    return currencyMap.count();
}
 
QVariant CurrencyModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();
 
    if (role == Qt::TextAlignmentRole) {
        return int(Qt::AlignRight | Qt::AlignVCenter);
    } else if (role == Qt::DisplayRole) {
        QString rowCurrency = currencyAt(index.row());
        QString columnCurrency = currencyAt(index.column());
 
        if (currencyMap.value(rowCurrency) == 0.0)
            return "####";
 
        double amount = currencyMap.value(columnCurrency)
                        / currencyMap.value(rowCurrency);
 
        return QString("%1").arg(amount, 0, 'f', 4);
    }
    return QVariant();
}
 
QVariant CurrencyModel::headerData(int section, Qt::Orientation /* orientation */, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();
    return currencyAt(section);
}
 
QString CurrencyModel::currencyAt(int offset) const
{
    return (currencyMap.begin() + offset).key();
}
 
void CurrencyModel::setCurrencyMap(const QMap<QString, double> &map)
{
    currencyMap = map;
    //reset(); // Нет метода в QT5
}

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    QMap<QString, double> currencyMap;
 
    currencyMap.insert("AUD", 1.3259);
    currencyMap.insert("CHF", 1.2970);
 
    currencyMap.insert("SGD", 1.6901);
    currencyMap.insert("USD", 1.0000);
 
    CurrencyModel currencyModel;
    currencyModel.setCurrencyMap(currencyMap);
 
    QTableView tableView;
    tableView.setModel(&currencyModel);
    tableView.setAlternatingRowColors(true);
 
    QVBoxLayout *vLayout = new QVBoxLayout();
    QHBoxLayout *hLayout = new QHBoxLayout();
 
    vLayout->addWidget(&tableView);
    hLayout->addLayout(vLayout);
    setLayout(hLayout);
}

CurrencyModel *currencyModel=new CurrencyModel;

void CurrencyModel::setCurrencyMap(const QMap<QString, double> &map)
{
    currencyMap = map;
    //reset(); // Нет метода в QT5
}

void CurrencyModel::setCurrencyMap(const QMap<QString, double> &map)
{
    beginResetModel();
    currencyMap = map;
    endResetModel();
}